1. Field of the Invention
The invention relates to electric cable gland assemblies.
2. Description of Related Art
A known type of cable gland assembly provides a barrier against leakage of liquid, gas or solid into the interstices of unfilled cables (i.e. cables which have voids or interstices within the cable between the cable cores and extending along its length) where the cable has had its outer sheath removed to enable the conductive elements of the cable cores to be connected to an item of electric equipment. The object of such cable glands is to avoid a flame path along the cable. Such cable gland assemblies are used in hazardous fire or explosion risk areas as are found on oil rigs for example. The invention relates particularly to cable gland assemblies of this type, wherein a hardenable compound is used to fill the space between and around the cable cores to prevent ingress of the liquid, gas or solid, the compound being contained within a sleeve or pot through which liquid, gas or solid, the compound being contained within a sleeve or pot through which the cores extend. Cable gland assemblies of this general type are known for example from GB 2 060 281A and GB 2 258 567 A.
Known compound sleeves or pots are made from metal, e.g. brass, or from rigid plastics material. Sleeves made of metal must be manufactured with precise tolerances. It is a burden to manufacture and check such high tolerances. Sleeves are also known which are provided with a separate seal, e.g. in annular form around the sleeve, to seal between the outer of the sleeve and the main body of the assembly.
An aim of the present invention is to provide at low cost a sleeve of simpler manufacture, construction and use.
It is also an aim of the present invention to improve the sealing of a sleeve.
According to the invention there is provided a cable gland assembly for an electric cable having a sheath enclosing at least one conductor core, the assembly comprising a body and a barrier sleeve locatable in the body wherein, in use, the at least one core extends through the body and the sleeve and a hardenable compound is disposed in the sleeve filling the sleeve and surrounding the at least one core, wherein the sleeve comprises a resilient or elastic material.
The resilient or elastic material preferably comprises a rubber or elastomer material. Further preferably, the sleeve substantially comprises a resilient or elastic material. More preferably, the sleeve completely comprises a resilient or elastic material.
The sleeve may be located with a compressed fit in the body i.e. with the resilient or elastic material, in use, located in the body under a degree of radial and/or axial deformation. An improved seal is thereby provided both between sleeve and body and sleeve and compound.
Advantageously, the sleeve in the invention is not required to be manufactured to the high tolerances of known sleeves. A suitable fit is easily achieved by the resilience or elasticity of the material.
The sleeve in the invention provides an improved seal between the outer of the sleeve and the inner of the assembly body. Since the sleeve comprises a resilient material, a seal between the outer of the sleeve and the inner of the assembly body is provided at least between a portion of the sleeve and the body, preferably between substantially the whole length of the sleeve and the body. In contrast, in the prior art, a separate annular seal is typically provided around the sleeve. Thus, the invention not only increases the degree of sealing, but it also replaces the separate two part construction of sleeve and seal with a single component.
The invention has also been found to be particularly advantageous in situations where the assembly may be subjected to considerable climate change, e.g. changes from high to low temperature and/or vice versa. With prior art sleeves there is always the possibility that the adhesion between the compound and sleeve may become reduced due to differing thermal expansion/contraction with potential compromise of the seal. However, in the invention, the sleeve comprising resilient or elastic material is able to deformably compensate for any loss of adhesion to provide a more consistent seal.
A yet further advantage is that if it is desired for any reason to remove the sleeve from the connector body, e.g. for inspection purposes, then the resilient material will allow a refitting of the sleeve in the connector body with little or no compromise in the quality of the seal either between sleeve and body or between sleeve and compound.
The sleeve of the invention is able to withstand cracking or melting over a wide range of temperatures. Preferably the sleeve of the invention is able to withstand temperatures from xe2x88x9260xc2x0 C. to +100xc2x0 C.
Preferably the sleeve material is not readily combustible.
The bore of the sleeve preferably has a frusto-conical shaped entry portion.
In many other respects the cable gland assembly of the invention may be constructed using known design features of cable glands.
Typically, the part of the assembly body in which the sleeve is located in use is an entry adapter, i.e. that part which connects to the equipment.
Preferably, the assembly comprises a camping spigot which, in use, is disposed at the frusto-conical end of the sleeve. Also, preferably, in use the spigot is urged against the sleeve by the engagement of a compression sleeve with the adaptor.
Further preferably the assembly comprises a clamping ring in use located annularly around a, typically complimentary shaped, surface of the spigot thereby to clamp an armour or earth element of the cable between the clamping ring and spigot.
The assembly also preferably further comprises a cap nut and outer cable seal to engage the exterior of the outer cable sheath by engagement of the cap nut with the compression sleeve.
The invention will now be described by way of the following examples and the accompanying drawings in which: